Abnormal and exaggerated deposition of extracellular matrix is the hallmark of all fibrotic diseases, including liver, pulmonary, kidney or cardiac fibrosis. The spectrum of affected organs, the progressive nature of the fibrotic process, the large number of affected persons, and the absence of effective treatment pose an enormous challenge when treating fibrotic diseases.
In an attempt to propose new therapeutic strategies for the treatment of fibrotic diseases, the inventors found that the compound 2-[(5-nitro-1,3-thiazol-2-yl)carbamoyl]phenyl]ethanoate (Nitazoxanide or NTZ), a synthetic antiprotozoal agent, also shows potent antifibrotic properties. Moreover, the evaluation of NTZ in a liver injury model revealed its capacity to reduce circulating bile acid concentration, thus reflecting its potential to treat both cholestatic (such as PBC and PSC) and fibrotic diseases.
NTZ, first described in 1975 (Rossignol and Caviar, 1975), was shown to be highly effective against anaerobic protozoa, helminths, and a wide spectrum of microbes including both anaerobic and aerobic bacteria (Rossignol and Maisonneuve, 1984; Dubreuil, Houcke et al., 1996; Megraudd, Occhialini et al., 1998; Fox and Saravolatz, 2005; Pankuch and Appelbaum, 2006; Finegold, Molitoris et al., 2009). It was first studied in humans for the treatment of intestinal cestodes (Rossignol and Maisonneuve, 1984) and it is now licensed in the United States (Alinia®, Romark laboratories) for the treatment of diarrhea caused by the protozoan parasites Crystosporidium parvum and Giardia intestinalis. NTZ has also been widely commercialized in Latin America and in India where it is indicated for treating a broad spectrum of intestinal parasitic infections (Hemphill, Mueller et al., 2006). The proposed mechanism of action by which NTZ exerts its antiparasitic activity is through the inhibition of pyruvate:ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reactions that are essential for anaerobic metabolism (Hoffman, Sisson et al., 2007). NTZ also exhibits activity against Mycobacterium tuberculosis, which does not possess a homolog of PFOR, thus suggesting an alternative mechanism of action. Indeed, it was shown that NTZ can also act as an uncoupler disrupting membrane potential and intra-organism pH homeostasis (de Carvalho, Darby et al., 2011).
The pharmacological effects of NTZ are not restricted to its antiparasitic activities and in recent years, several studies revealed that NTZ can also confer antiviral activity (Di Santo and Ehrisman, 2014; Rossignol, 2014). NTZ interferes with the viral replication by diverse ways including a blockade in the maturation of hemagglutinin (influenza) or VP7 (rotavirus) proteins, or the activation of the protein PKR involved in the innate immune response (for a review, see (Rossignol, 2014)). NTZ was also shown to have broad anticancer properties by interfering with crucial metabolic and prodeath signaling pathways (Di Santo and Ehrisman, 2014)
In this invention, using a phenotypic screening assay to identify potential antifibrotic agents, it was discovered that NTZ or its active metabolite Tizoxanide (or TZ) interferes with the activation of hepatic stellate cells (HSC), which play a key role in the development of hepatic fibrosis. This effect was totally unexpected in view of the properties previously reported for these molecules. Moreover, NTZ and TZ were shown to interfere with the activation of stimulated fibroblasts derived from other organs such as heart, lung and intestines. The antifibrotic properties of NTZ was further confirmed in a preclinical model of liver disease (CDAAc diet-induced NASH) by showing significant reduced levels of hepatic collagen and fibrosis. In addition to its antifibrotic activity, NTZ was also shown to reduce circulating bile acid concentration in a CCl4-induced liver injury model. NTZ and TZ thus appear as compounds of interest for the treatment of cholestatic diseases and diverse types of fibrotic diseases.